It seems the UK isn't a nation of clockwatchers. Photograph: Getty Images

Bosses are getting £25bn of work out of us for nothing, according to a report published today by the TUC. Almost 5 million of us are doing around seven hours of unpaid overtime a week - work that is worth almost £5,000 over the course of a year, it says.

With many of us working five-day weeks, that's approaching two hours extra a day we're putting in for, well, for what? The survey only looks at how much we are working, not why, or in what careers people are putting in the most hours. It doesn't compare how much overtime people at different levels of seniority are doing, or show how much more or less overtime is being worked by people who do get paid for those extra hours.

In fact it raises a lot of questions. Are people working those extra hours because they are scared that if they don't, someone else will and they might lose their job? Is it because their manager has an unrealistic expectation of how much work they can get done in a day? Is it because they're ambitious and want to do extra work to get on? Or is it simply that they have got into the habit of arriving early or leaving late?

Are you one of the 5 million workers who do put it in extra hours, and if you are, why do you do it?